Electrode system



June 6, 1939.

EEEEEEEEEEEEE EM 279/! [VIII/II IZ gIZ i INVENTOR GEE Patented June 6, 1939 UNITED STATES PATENT OFFICE susc'raons SYSTEM Application July 21, 1936, Serial No. 91,800

Germany July 29, 1935 9 Claims.

This invention relates to an electrode system for rectifying highor medium frequency electriof the system.

cal oscillations, in which the positive and negative electrodes consists of layers of materials having a very different emitting capacity with respect to one another and being separated by, a solid insulating layer.

The invention has for its object to provide a low and exactly repr'oducable self-capacity in such an electrode system.

It has already been proposed to provide a conical lead contact on a graphite layer which is used as a supply conductor in a cuprous oxide detector. In this case-the capacity is determined by the surface of the graphite layer bearing the v lead contact. It is very difficult to obtain a small surface capable of being reproduced with the aid of such a layer and in addition not all of the main factors determining the value of the capacity are influenced in this manner.

Indeed, it is to be considered that the capacity is determined not only by the surface of the conducting parts in the electrode system, but that it also depends on the thickness of the insulating layer between the conductive parts. A

For this reason it is impossible previously to determine the capacity in a cuprous oxide detector.

since the size of the. contact surfaces of the conducting parts in the system can be controlled to a greater or less degree, but one can never establish beforehand the thickness of the stoichiometrically correct cuprous oxide layer after oxidation of the copper base, for the insulating separation layer, i. e. the insulating coating, between the electrodes is formed simultaneously with the semi-conductive electrode, so that the thickness of these layers separately can practically not be controlled.

According to the invention it is possiblepre-l viously to fix the capacity of an electrode system for rectifying or controlling highor medium frequency oscillations. This is effected by using the combination of an insulating coating separately provided between the electrodes and of a limited contact surface of 10 mm at the most for at least one of theparts influencing the capacity A separately arranged insulating coating has the advantage that it can be provided in any deinvention has the great advantage of the selfcapacity being entirely known before the construction of the system and does not depend on some uncontrollable factor or other.

Furthermore it has already been suggested to constitute the detector in a radioset by a crystal.

However, a crystal detector has a rectifying effect only at one or a few points of the crystal surface and more particularly where the surface bears an insulating coating having such a thickness that its resistance does not have an excessive value and corresponds to the applied voltage to be rectified. Thus, in order that a crystal can be .used as a detector the surface of the crystal should be scanned with the aid of a pointed metal contact till a point having a rectifying efiect will have been found. Also in this casethe value of the capacity can not possibly be predetermined.

These drawbacks are not inherent to electrode systems, according to the invention. In these systerns every point of theinsulating coating has a rectifying effect where one of the terminal electrodes extends opposite the other terminal electrode.

The invention permits the self-capacity to be rendered extremely low, for'at least one of the contacts is given as small as possible a surface, whereas the thickness of the insulating coating is reduced as much as possible, but so that the-risk of a breakdown is avoided at the normally applied voltage. The means which, according to the in vention are used, in combination for ensuring the desired effect allow, in contradistinction' to the prior art, to predetermine and to ensure, even in mass production, the definite reproducible value of the self-capacity for such a cell. Especially the reproducibility is of great importance in view of the fact that the self-capacity exerts a definite influence on a circuit comprising the cell. In order to achieve the most favourable efi'ect in such a circuit certain measures should be taken in designing it. If the self-capacity of the various cells would be different with respect to one another than in spite of the fact of certain measures having been takemthe latter would be of no avail when the initial cell adapted to the circuit would be replaced by another one.

The invention will be more clearly understood by reference to the accompanying drawing representing, by way of example, a few embodiments thereof shown in section. v

The first form of construction shown in Figure 1 concerns anelectrode system comprising a separately provided insulating coating of silicon dioxide whereas the good-conductive electrode has a limited contact surface. In this figure the copper base I bears the semi-conductive electrode 2 of cuprous sulphide (CUzS) which is applied by pressing. The insulating coating 3 is formed on the semi-conductor by evaporating a dosage of silicon dioxide (SiOz), for instance, up to a thickness of 5 On to this insulating coating the good-conductive electrode 4 is applied which consist of iron and whose contact has a small surface of say 0.25 mm.

In this case the capacity of this system is determined by the thickness of the SiOz layer and the size of the contact surface of the iron 4. Both values are well in hand. In practice the capacity of such a system amounting, for instance, to 7.5 cm. is ensured in a perfectly regular and reproducible manner for any individual system in mass production.

In practice the deviations amount only to a few per cent, of the desired correct value.

The same holds good for the following embodiments.

The second embodiment concerns an electrode system wherein the good-conductive electrode 5 (vide-Figure 2) consists of aluminum. The latter is electrochemically provided with an insulating coating 6 consisting of amorphous or crystalline aluminum oxide (A1203). For the semiconductor 1 molybdenum sulphide (M082) is used, which is applied on to the insulating coating by pressing. In order to limit the self-capacity of the system the contact surface of the supply conductor 8 is limited by forming it from a thin copperwire whose normal cross-section does not exceed 0.3 mm. Due to the large resistance of the semi-conductor I it may be taken that only that column of the layer I practically partakes in the conduction, which forms the extension of the supply conductor 8, so that the capacity is influenced only by the terminal surface of said column. In this case the supply conductor 8 is consequently really the part influencing the capacity of the system, since the capacity depends on the size of itscontact surface.

The thickness of the insulating coating can be previously fixed, it being possible when forming this layer electrochemically to calculate its'thickness from the forming current used and from the duration, the choise of the electrolyte being taken into account. Thus the self-capacity is exactly determined also in this case.

The third embodiment concerns an electrode system comprising a semi-conductive electrode of selenium.

On to a brassplate 9 selenium I0 is applied in the liquid state and smoothly painted thereon to a thickness of 0.03 mm. The aggregate is introduced into a furnace and heated for sometime (say-2 to 24 hours) at a temperature of about 200 C. This treatment serves for converting the selenium from the amorphous state into the conductive crystalline modification.

The electro-positive electrode is constituted by an iron wire II which has a surface of 0.25 mm. at the bottom. This surface and, if necessary, a part along the lateral surface of the wire is coated with insulating coating material H which may consist of artificial resin such as polystyrene, whereupon the wire is arranged on the selenium with the flatsurface'coated with polystyrene.

What I claim is:

1. An electrode system comprising, a metallic carrier, a layer of semi-conducting material formed on one face of the carrier, a metallic rod one end of which has a limited surface area which is a small fraction of the area of said face of the carrier, and a layer of insulating material interposed between and in contact with both of said end surfaces of the metallic rod and the semi-conducting material.

2. An electrode system comprising, a metallic carrier; 9. layer of semi-conducting material formed on one face of the carrier, a coating of insulating material formed on the free face' of the semi-conducting material and a metallic rod, one end of which has a limited surface area in contact with the insulating coating, said contacting area being of the order of 0.25 mm..

3. A dry rectifier cell having asymmetrical conductivity characteristics comprising a layer of semi-conducting material, a layer of insulating material covering at least a portion of one face f the semi-conducting material, a metallic el trode in contact with the exposed face of t e layer of insulating material, and a metallic 1' having an end surface area of the order of 0.25 square millimeter, said end surface bearing on said semi-conducting material.

4. A dry rectifier cell having asymmetrical conductivity characteristics comprising a brass plate arranged so as to serve both as a carrier and as a supply conductor, a layer of semi-conducting material comprising cuprous sulphide on a face of said plate, a coating of insulating material comprising silicon dioxide borne on the free face of the semi-conducting material and an iron rod tapered at one end to an end area of about 0.25 square millimeter, said tapered end of the iron rod bearing on the insulating coating.

5. A dry rectifier comprising an aluminum electrode having a substantially planar surface, a layer of aluminum oxide formed on said surface, a substantially cylindrical copper electrode and a filler interposed between and in contact with said copper electrode and said layer of aluminum oxide, said filler being composed of molybdenum sulphide and a layer of amorphous or crystalline aluminum oxide. y

6. A dry rectifier comprising a substantially planar aluminum electrode, a layer of aluminum oxide on a face of said electrode, a layer of molybdenum sulphide on the exposed side of the layer of aluminum oxide and a copper electrode borne on the exposed side of said layer of molybdenum sulphide, said copper electrode having a contact surface with said molybdenum sulphide of the order of 03 square millimeter.

7. A dry rectifier comprising a substantially planar copper electrode, a layer of cuprous sulphide on said planar face of said electrode, a layer of silicon dioxide on the side of the layer of cuprous sulphide which is in contact with the copper plate and an iron conducting element in contact with an area of the side of said layer of silicon dioxide which is not in contact with the cuprous sulphide, said contact layer being of the order .of 0.25 square millimeter.

8. A dry rectifier comprising a brass electrode having a substantially planar face, a layer of selenium on said planar face of the brass electrode, an iron wire comprising the electro-positive electrode of the dry rectifier, a layer of insulation material interposed between an end; of said iron wire and the layer of selenium;

9. A dry rectifier comprising in combination, a substantially planar brass electrode, a layer of selenium on the surface of said plate and an iron wire insulatingly mounted on said plate through the intermediary of a thin layer of polystyrene located at least between the contact surface of the iron wire and the selenium.

WILLEM CHRISTIAAN vm GEEL. 

